Plastic/metal composite stress plate and method of using same for securing a thermoplastic roof membrane to a roof deck

ABSTRACT

A two-piece fastener assembly for securing thermoplastic roof membranes to an underlying roof deck having: a metal stress plate coated with a thermoplastic coating on its top surface; an opening in the center portion of the stress plate; and a fastener positioned in the opening of the stress plate for securing the stress plate and one thermoplastic roof membrane to the underlying roof deck. In a method aspect the steps of securing thermoplastic roof membranes to an underlying roof deck, includes: placing a first thermoplastic roof membrane on the roof deck; placing a line of stress plates on the marginal portion of the first thermoplastic roof membrane and securing the stress plates along with the first thermoplastic roof membrane to the roof deck by use of the fastener; placing a second thermoplastic roof membrane to overlap the line of stress plates and the marginal portion of the first thermoplastic roof membrane; and applying heat and pressure to the line of stress plates and the overlapped portion of the first and second thermoplastic roof membranes to fuse them together and provide a waterproof covering over the roof deck.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to fasteners employed to fasten acovering material to an underlying substrate. More particularly, theinvention relates to a plastic/metal composite stress plate with afastener for fastening a membrane, such as a roof membrane or roofinginsulation, to a roof deck, a wall, concrete, steel, stone, plaster, orwood.

[0003] 2. Reported Development

[0004] Fasteners are conventionally employed in the building industryfor fastening or clamping a flexible membrane, such as an insulationmembrane to a substrate, such as a roof deck. The fasteners typicallycomprise a large head portion and a shank portion. In use, the shankportion is driven through the membrane into the underlying substrate toanchor the fastener thereinto, while the head portion holds the membraneagainst the substrate and prevent removal thereof by wind lift. Theundersurface of the head portion is typically provided with grippingmeans so that the membrane is prevented from moving or sliding under thefastener. The gripping means are typically designed not to penetratecompletely through the membrane in order to prevent atmospheric moisturefrom entering into the substrate through the holes which tend to be madeby the gripping means. It is also important that the gripping means arespread/distributed in the undersurface of the head portion of the stressplate in order prevent tearing of the membrane. Conventional fastenersare illustrated by the following references.

[0005] U.S. Pat. No. 4,787,188 discloses a stress plate for securing aroof membrane to a roof deck. The stress plate is circular having a topsurface and a bottom surface with a central circular opening forreceiving a screw for fastening the stress plate over a roof membraneand to the roof deck. The stress plate is equipped with four grippingprongs of triangular shape which are circumferentially spaced from eachother by 90°.

[0006] In use a first membrane is applied to a roof deck surface, thenthe membrane is secured to the roof deck surface with the stress plateand the screw. A top sheet or membrane is lapped over the first membraneto cover the stress plate and welded to the first membrane. The fourgripping prongs in the stress plate grip the first sheet and hold thesame on top of the roof deck without tearing.

[0007] U.S. Pat. No. 5,049,018 discloses a fastener for gripping asubstrate material. The fastener is of a unitary piece comprising a headportion, a shaft portion, and a hook portion at the end of the shaftportion, wherein the hook portion has an outwardly and upwardlyextending resilient end portion. The end portion has an end surfacewhich provides gripping contact with a wall of a hole in a substrateinto which the fastener is inserted.

[0008] U.S. Pat. No. 5,163,798 relates to a fastener assembly which isemployed to secure plies or membranes of roofing, felt and paper toprevent the materials from being blown off the base roofing materialbefore the base material is sufficiently hardened.

[0009] The assembly comprises a fastener and a retainer plate. Theassembly includes a fastener plate which defines a substantiallyrectangular opening. The fastener includes a head and a pair of legswhich are integrally hingably connected to the head. The legs have acontoured distal portion and an angular side configuration so that atleast one of the legs is forced apart as the fastener is driven into thebase material.

[0010] We have observed that under windy conditions the prior artfasteners need improvement in securely holding a flexible membrane on asubstrate without the gripping means penetrating the flexible membrane,and without tearing the flexible membrane.

[0011] Accordingly, an object of the present invention is to provide anew and improved stress plate with a fastener to allow attachment of oneor more flexible membranes to an underlying substrate without tearingthe flexible membrane or allowing it to slip out from under the stressplate.

[0012] In another aspect, the present invention relates to a method forsecuring thermoplastic roof membranes to a roof deck using a stressplate and fastener and fusing overlapping portions of two roof membranesto provide a waterproof covering over a roof deck.

[0013] Asphalt roof membranes to prevent moisture from entering into anunderlying roof deck are being replaced by thermoplastic sheet materialswhich offer a superior, longer-lasting roof at a lower cost. In theprocess of installing thermoplastic sheet materials over a roof deck,the typical steps are as follows. A first sheet is laid adjacent to thelower edge of the roof and running parallel thereto. Fastening means,such as batten bar or a line of stress plates are positioned neat theupper edge of the first sheet. Fasteners are inserted through the battenbar or stress plates and into the roof deck to securely hold the firstsheet to the roof deck. Then a second sheet is laid over the roof deckin a marginally overlapping relationship with the first sheet. Thesecond sheet also overlaps the batten bar or the line of stress plates.The overlapping edge area of the second sheet overlaps the area of thefirst sheet on both sides of the batten bar or line of stress plates. Aweld is then applied between the first sheet and the second sheetresulting in the fusion of the two sheet on both sides of the batten baror the line of stress plates. The weld is applied by the use of awelding machine or tool which softens the thermoplastic sheets and,after cooling, solidifies and forms a continuous sheet. The steps arerepeated until the roof deck is completely covered by the thermoplasticsheets.

[0014] It has been observed that stress plates having a high profilecreate bumps in the weld area. It has also been observed that stressplates made of metals do not adhere to the second or overlappingthermoplastic sheet thereby creating bubbles in the weld. Accordingly,it is another object of the present invention to provide a low profilestress plate which substantially remains in the plane of thethermoplastic sheets and which is coated with a thermoplastic materialso that the second or overlapping sheet is also welded to the stressplate.

[0015] These and other aspects will be addressed as the description ofthe invention proceeds.

SUMMARY OF THE INVENTION

[0016] In the device aspect, the present invention comprises twonon-integral components: a plastic coated metal stress plate and afastener. The stress plate has a top surface and a bottom surface andincludes an opening in its center portion to allow a fastener, such as ascrew, therethrough for attachment of the stress plate to an underlyingsubstrate, such as a roof deck. The opening may be circular orrectangular. The top surface of the stress plate is coated with athermoplastic coat, such as polyvinyl chloride, thermoplastic olefins,chlorinated polyethylene, chlorosulfonated polyethylene, nylon andethylene propylene diene rubber. The stress plate has a low heightprofile so that an installation over a thermoplastic sheet preferablywill not produce bumps therein. To achieve this objective, the totalheight of the uncoated stress plate will preferably be of from about0.025″ to about 0.250″ and more preferably about 0.125″ to 0.200″.

[0017] In the method aspect, the present invention comprises the stepsof:

[0018] a) laying a first thermoplastic sheet or membrane on a portion ofthe roof deck;

[0019] b) laying a line of stress plates near the edge of thethermoplastic sheet or membrane parallel to the edge;

[0020] c) securing the thermoplastic sheet or membrane on the roof deckby inserting fasteners through the stress plates, the firstthermoplastic sheet or membrane and into the roof deck;

[0021] d) laying a second thermoplastic sheet or membrane on the roofdeck in an overlapping relationship to the line of stress plates and thefirst thermoplastic sheet or membrane; and

[0022] e) applying heat and pressure to the overlapped portion of thethermoplastic sheets or membranes on both sides of the line of stressplates and over the line of stress plates thereby causing a fusion ofthe thermoplastic sheets or membranes and to the line of the stressplates.

[0023] The heat weld may be accomplished by a welding machine known inthe art, such as described in U.S. Pat. Nos. 4,259,142, 4,289,552,4,440,588, 4,533,423, 4,861,412, 4,894,112, 5,110,398, and 5,935,357.However, we prefer top use a welding machine which is disclosed inco-pending application Ser. No. 09/190,373 and comprises a pressureroller and a heating element for a welding apparatus for producing aweld simultaneously on each side of a line of fasteners and over thefasteners. The pressure roller is integral with an axle designed to beconnected to a driving means at one end thereof; at the other end of theaxle the pressure roller comprises a distal end, a proximal end and acenter portion which defines a groove between the proximal and distalends. The groove of the pressure roller carries an elastomeric cushiondesigned to smoothly ride over a line of fastening means, and form acontinuous weld in between the fastener plates.

[0024] The pressure roller is used in combination with a heating elementcontaining a blower which forces heated air through a nozzle. The nozzlehaving an outlet therein comprises three portions: two large openingportions and a restricted opening portion therebetween. In use, thelarge opening portions allow delivery of the major portion of the hotair produced by the heating element while the restricted opening stillallows delivery of sufficient amounts of the heated air to soften andfuse the overlapping portions of the thermoplastic sheet.

[0025] The stress plate of the present invention may be of circular,ellipsoidal, square, or rectangular configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a top, perspective view of the circular plastic/metalcomposite stress plate with a fastener;

[0027]FIG. 2 is a side elevational view thereof, all other sides beingidentical thereto;

[0028]FIG. 3 is a top plan view thereof;

[0029]FIG. 4 is a bottom perspective view thereof,

[0030]FIG. 5 is a top perspective view of the ellipsoidal plastic/metalcomposite stress plate with a fastener;

[0031]FIG. 6 is a side elevational view thereof;

[0032]FIG. 7 is another side elevational view thereof;

[0033]FIG. 8 is a top plan view thereof;

[0034]FIG. 9 is a bottom perspective view thereof;

[0035]FIG. 10 is a top perspective view of the square plastic/metalcomposite stress plate with a fastener;

[0036]FIG. 11 is a side elevational view thereof, all other sides beingidentical thereto;

[0037]FIG. 12 is a top plan view thereof;

[0038]FIG. 13 is a bottom perspective view thereof;

[0039]FIG. 14 is a top perspective view of the rectangular plastic/metalcomposite stress plate with a fastener;

[0040]FIG. 15 is a side elevational view thereof;

[0041]FIG. 16 is another side elevational view thereof;

[0042]FIG. 17 is a top plan view thereof;

[0043]FIG. 18 is a bottom perspective view thereof;

[0044]FIG. 19 is a is a cross-sectional view illustrating the use of thestress plate and the fastener for attaching roof membranes to a roofdeck.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Reference is now being made to the drawings wherein like numeralsrepresent like parts throughout the figures showing the variousembodiments of the present invention.

First Embodiment—Circular Stress Plate With Fastener

[0046]FIGS. 1-4 relate to the first embodiment of the present inventionin which the circular stress plate is generally designated at 10 and thefastener is generally designated at 12. The components are non-integraland, when put together, constitute the invention. The circular stressplate 10 has a round or rectangular opening 14 in its center portionthrough which the fastener is inserted when the stress plate is employedfor attaching and firmly holding a roof membrane to an underlying roofdeck. The stress plate has a circular body with a top surface and abottom surface and characterized by

[0047] a) a diameter of from about 1″ to about 4″ or more, andpreferably about 2″;

[0048] b) an opening 14 in its center portion the diameter of which isabout 0.25″;

[0049] c) a first flat surface 16 surrounds the opening having a radiusof about 0.25″ which is designed to receive the head portion 18 offastener 12 without passing through said opening 14;

[0050] d) a second flat surface 20 adjacent to the circumferential edge28 having a radius of from about 0.12″ to about 0.25″, and preferablyabout 0.20″;

[0051] e) a third flat surface 22 extends between the first flat surface16 and the second flat surface 20 having a radius of from about 0.25″ toabout 1.0″, and preferably about 0.50″;

[0052] f) connecting the second flat surface 20 with third flat surface22, a first circumferential portion 24 extends above the second flatsurface and towards third flat surface at an angle of from about 25° toabout 70°, and preferably at about 45°; and

[0053] g) connecting the first flat surface 16 and the third flatsurface 22 a second circumferential portion 26 extends above the firstflat surface and towards the third flat surface at an angle of fromabout 25° to about 70°, and preferably at about 45°.

[0054] The distance between the first flat surface 16 and the third flatsurface 22 is of from about 0.025″ to about 0.100″, and preferably about0.050″ to 0.070″. The distance between the second flat surface 20 andthe third flat surface 22 is also of from about 0.025″ to about 0.100″,and preferably about 0.050″ to about 0.070″.

[0055] The composition of the stress plate consists of a metal, such assteel, galvalume or galvanized metals, preferably having a thickness ofabout 0.025″ to 0.250″; and a thermoplastic layer coated on the topsurface of the metal plate preferably having a thickness of about 0.005″to 0.100″. The thermoplastic coat completely covers the top surface ofthe stress plate, namely the first, second, and third flat surfaces andthe first and second circumferential portions which connect the first,second and third flat surfaces. The total height of the coated stressplate is preferably about 0.030″ to 0.350″.

Second Embodiment—Ellipsoidal Stress Plate With Fastener

[0056]FIGS. 5-9 relate to the second embodiment of the present inventionin which the ellipsoidal stress plate is generally designated at 10′ andthe fastener is generally designated at 12′ The two components arenon-integral and, when put together, constitute the invention. Theellipsoidal stress plate 10′ has a round or rectangular opening 14′ inits center portion through which the fastener is inserted when thestress plate is employed for attaching and firmly holding a roofmembrane to an underlying roof deck. The stress plate has an ellipsoidalbody with a top surface and a bottom surface and is characterized by:

[0057] a) a larger diameter of from about 1″ to about 4″ or more, andpreferably about 2″;

[0058] b) a smaller diameter of from about 0.5″ to about 2″, andpreferably about 1.5″;

[0059] c) an opening 14′ in its center portion the diameter of which isabout 0.25″;

[0060] d) a first flat surface 16′ surrounds the opening having a largerradius of about 0.25″ and a smaller radius of about 0.15″ which isdesigned to receive the head portion 18′ of the fastener 12′ withoutpassing through said opening 14′;

[0061] e) a second flat surface 20′ adjacent to the circumferential edge28′ having a larger radius of from about 0.12″ to about 0.25″, andpreferably about 0.20″, and a smaller radius of about 0.15″ to 20″;

[0062] f) a third flat surface 22′ extends between the first flatsurface 16′ and second flat surface 20′ having a larger radius of fromabout 0.25″ to about 0.75″, and preferably about 0.50″ and a smallerradium of about 0.15″;

[0063] g) connecting the second flat surface 20′ with the third flatsurface 22′ a first circumferential portion 24′ extends above the secondflat surface and towards the third flat surface at an angle of fromabout 25° to about 70°, and preferably at about 45°; and

[0064] h) connecting the first flat surface 16′ and the third flatsurface 22′ a second circumferential portion 26′ extends above the firstflat surface and towards the third flat surface at an angle of fromabout 25° to about 70°, and preferably at about 45°.

[0065] The distance between the first flat surface 16′ and the thirdflat surface 22′ is of from about 0.025″ to about 0.100″, and preferablyabout 0.050″ to 0.070″. The distance between the second flat surface 20′and the third flat surface 22′ is also of from about 0.025″ to about0.100″, and preferably about 0.050″ to about 0.070″.

[0066] The composition of the stress plate consists of a metal, such assteel, galvalume or galvanized metals, having a thickness of about 1 to3 mm; and a thermoplastic layer coated on the top surface of the metalplate having a thickness of about 0.5 mm to 2.0 mm. The thermoplasticcoat completely covers the top surface of the stress plate, namely thefirst, second, and third flat surfaces and the first and secondcircumferential portions which connect the first, second and third flatsurfaces. The total height of the coated stress plate is preferablyabout 0.030″ to 0.350″.

Third Embodiment—Square Stress Plate With Fastener

[0067]FIGS. 10-13 relate to the third embodiment of the presentinvention in which the square stress plate is generally designated at 30and the fastener is generally designated at 32. The components arenon-integral and, when put together, constitute the invention. Thesquare stress plate 30 has a round or rectangular opening 34 in itscenter portion through which the fastener is inserted when the stressplate is employed for attaching and firmly holding a roof membrane to anunderlying roof deck. The stress plate has a square body with a topsurface and a bottom surface and is characterized by:

[0068] a) a larger diameter of from about 1″ to about 4″ or more, andpreferably about 2″;

[0069] b) an opening 34 in its center portion the diameter of which isabout 0.25″;

[0070] c) a first flat surface 36 surrounds the opening having a radiusof about 0.25″ which is designed to receive the head portion 38 of thefastener 32 without passing through said opening 34;

[0071] d) a second flat surface 40 adjacent to the parametrical edge 48having a radius of from about 0.12″ to about 0.25″, and preferably about0.20″;

[0072] e) a third flat surface 42 extends between the first flat surface36 and second flat surface 40 having a radius of from about 0.25″ toabout 0.75″, and preferably about 0.50″;

[0073] f) connecting the second flat surface 40 with the third flatsurface 42 a first circumferential portion 44 extends above the firstflat surface and towards the third flat surface at an angle of fromabout 25° to about 70°, and preferably at about 45°; and

[0074] g) connecting the second flat surface 40 and the third flatsurface 42′ a second parametrical portion 46 extends above the secondflat surface and towards the third flat surface at an angle of fromabout 25° to about 70°, and preferably at about 45°.

[0075] The distance between the first flat surface 36 and the third flatsurface 42 is of from about 0.025″ to about 0.100″, and preferably about0.050″ to 0.070″. The distance between the second flat surface 40 andthe third flat surface 42 is also of from about 0.025″ to about 0.100″,and preferably about 0.050″ to about 0.070″.

[0076] The composition of the stress plate consists of a metal, such assteel, galvalume or galvanized metals, having a thickness of about 1 to3 mm; and a thermoplastic layer coated on the top surface of the metalplate preferably having a thickness of about 0.005″ to 0.100″. Thethermoplastic coat completely covers the top surface of the stressplate, namely the first, second, and third flat surfaces and the firstand second parametrical portions which connect the first, second andthird flat surfaces. The total height of the coated stress plate ispreferably about 0.030″ to 0.350″.

Fourth Embodiment—Rectangular Stress Plate With Fastener

[0077]FIGS. 14-18 relate to the fourth embodiment of the presentinvention in which the rectangular stress plate is generally designatedat 30′ and the fastener is generally designated at 32′. The componentsare non-integral and, when put together, constitute the invention. Thestress plate 30′ has a round or rectangular opening 34′ in its centerportion through which the fastener is inserted when the stress plate isemployed for attaching and firmly holding a roof membrane to anunderlying roof deck. The stress plate has a rectangular body with a topsurface and a bottom surface and is characterized by:

[0078] a) a larger diameter of from about 1″ to about 4″ or more, andpreferably about 2″;

[0079] b) a smaller diameter of from about 0.5″ to about 2″, andpreferably about 1.5″;

[0080] c) an opening 34′ in its center portion the diameter of which isabout 0.25″;

[0081] d) a first flat surface 36′ surrounds the opening having a largerradius of about 0.25″ and a smaller radius of about 0.15″ which isdesigned to receive the head portion 38′ of the fastener 32′ withoutpassing through said opening 34′;

[0082] e) a second flat surface 40′ adjacent to the parametrical edge48′ having a larger radius of from about 0.12″ to about 0.25″, andpreferably about 0.20″, and a smaller radius of about 0.15″ to 20″;

[0083] f) a third flat surface 42′ extends between the first flatsurface 36′ and second flat surface 40′ having a larger radius of fromabout 0.25″ to about 0.75″, and preferably about 0.50″ and a smallerradius of about 0.15″ to 20″

[0084] g) connecting the second flat surface 40′ with the third flatsurface 42′ a first parametrical portion 44′ extends above the firstflat surface and towards the third flat surface at an angle of fromabout 25° to about 70°, and preferably at about 45°; and

[0085] h) connecting the second flat surface 40′ with the third flatsurface 42′ a second parametrical portion 46′ extends above the secondflat surface and towards the third flat surface at an angle of fromabout 25° to about 70°, and preferably at about 45°.

[0086] The distance between the first flat surface 36′ and the thirdflat surface 42′ is of from about 0.025″ to about 0.100″, and preferablyabout 0.050″ to 0.070″. The distance between the second flat surface 40′and the third flat surface 42′ is also of from about 0.025″ to about0.100″, and preferably about 0.050″ to about 0.070″.

[0087] The composition of the stress plate consists of a metal, such assteel, galvalume or galvanized metals, preferably having a thickness ofabout 0.025″ to 0.250″; and a thermoplastic layer coated on the topsurface of the metal plate preferably having a thickness of about 0.005″to 0.100″.

[0088] Softer metals such as copper and aluminum may also be used,however, the thickness of the stress plate should be larger to providesufficient integrity to the stress plate. The fastener is typically ascrew of 2 to 3 inches long having threads thereon.

[0089] The thermoplastic coat completely covers the top surface of thestress plate, namely the first, second and third flat surfaces and thefirst and second parametrical portions which connect the first, secondand third flat surfaces. The total height of the coated stress plate ispreferably about 0.030″ to 0.350″.

[0090] The low profile of the four embodiments of the present inventioninsures that when a second membrane covers the line of stress plates, noobjectionable bumps are created, to wit, the stress plates substantiallyremain in the plane of the membranes.

[0091]FIG. 19 is a cross-sectional view illustrating the use of thestress plate and the fastener for attaching a roof membrane to a roofdeck. Lower thermoplastic membrane 50 is positioned over insulation 52which is over the roof deck surface 54. The fastener 56 is then insertedthrough stress plate 58, insulation 52, and into roof deck 54. Upperthermoplastic membrane 60 is then lopped over the marginal portions ofthe lower membrane covering the stress plate 58. Upper membrane 60 issecured to the stress plate and the lower membrane by welded seam 62.

[0092] Wind Uplift Test Comparative wind uplift tests were conducted ona 2″ diameter circular composite stress plate versus a standard 2″diameter circular metal plate without thermoplastic coating thereon. Thewind uplift test measures the resistance of the roofing system to highwind currents. For example, a three second burst of wind at 175 milesper hour can exert a negative pressure of 90 pounds per square foot onthe roof system.

[0093] The composite circular stress plate consisted of a stainlesssteel plate coated with polyvinyl chloride; while the standard metalstress plate had no coating thereon.

[0094] A) Composite Stress Plate

[0095] The roofing system consisted of: a roof deck, an insulating layerplaced on the roof deck, and a thermoplastic roof membrane placed on thetop of the insulating layer. A line of composite stress plates wasplaced on the marginal area of the thermoplastic layer spaced 6″ apartfrom each other. The composite stress plates were then attached to theroof system by inserting the fasteners through the stress plates, theroofing membrane, and insulating layer and into the roof deck. A secondroofing membrane was then placed on the first roofing membrane in amarginally overlapping position to the first roofing membrane and theline of stress plates. The overlapping portions of the first and secondmembranes were about 5- 6″ wide. The welding was accomplished bysubjecting the overlapped portions to heat, softening them to a weldableconsistency and pressing them together by an apparatus having a heat andpressure means. After the overlapped portions of the membranes cooled, asolid seal was formed and the welded are was subjected to wind uplifttest. The wind uplift test at 60 seconds showed 180 pounds of pressureper square foot.

[0096] The testing was repeated using the same materials, conditions andprocesses except that the composite stress plates were spaced every 12″apart from each other. The wind uplift test at 60 seconds showed 105pounds of pressure per square foot.

[0097] B) Standard Metal Stress Plate

[0098] Wind uplift tests were conducted using the same materials,conditions and processes described in (A) above, except instead of thecomposite stress plate of the present invention a standard stainlesssteel stress plate was used. The stainless steel stress plates spacedevery 6″ from each other showed a wind uplift at 60 seconds 150 poundsof plates pressure per square foot, and when the stainless steel stressplates were spaced 12″ from each other, the wind uplift test at 60seconds was found to be 75 pounds of pressure per square foot. PARTSLIST First and Second Embodiments Circular and ellipsoidal stressplates, 10, 10′ generally designated Fastener, generally designated 12,12′ Opening in center portion of stress plate 14, 14′ First flat surface16, 16′ Head portion of fastener 18, 18′ Second flat surface 20, 20′Third flat surface 22, 22′, First circumferential portion 24, 24′ Secondcircumferential portion 26, 26′ Circumferential edge of stress plate 28,28′ Second and Third Embodiments Square and rectangular stress plate,30, 30′ generally designated Fastener, generally designated 32, 32′Opening in center portion of stress plate 34, 34′ First flat surface 36,36′ Head portion of fastener 38, 38′ Second flat surface 40, 40′ Thirdflat surface 42, 42′ First parametrical portion 44, 44′ Secondparametrical portion 46, 46′ Parametrical edge of stress plate 48, 48′Using the Stress Plate Lower thermoplastic membrane 50 Insulation 52Roof deck 54 Fastener (screw) 56 Stress plate 58 Upper thermoplasticmembrane 60 Welded seam 62

[0099] In a preferred embodiment, this invention can be practiced inconjunction with the fasteners described in U.S. patent application Ser.No. 10/357,113, filed Feb. 3, 2003, the disclosure of which is herebyincorporated by reference in its entirety. Such fasteners featuremultiple pairs of barbs extending downward from the bottom surface ofthe fastener plate and provide further resistance to wind uplift.

[0100] Having described the invention with reference to its preferredembodiments, it is to be understood that modifications within the scopeof the invention will be apparent to those skilled in the art.

What is claimed is:
 1. A two-piece fastener assembly for securing twothermoplastic roof membranes to an underlying roof deck comprising: a) ametal stress plate of circular configuration defined by a top surfaceand a bottom surface having an opening in its center portion forreceiving a fastener therethrough; b) a thermoplastic coating coveringthe top surface of said metal stress plate; and c) a fastener positionedin said opening of said metal stress plate.
 2. The two-piece fastenerassembly of claim 1 wherein said metal stress plate is formed ofstainless steel, galvalume or galvanized metals.
 3. The two-piecefastener assembly of claim 1 wherein said thermoplastic coating is amaterial selected from a group consisting of polyvinyl chloride,thermoplastic olefins, chlorinated polyethylene, chlorosulfonatedpolyethylene, nylon and ethylene propylene diene rubber.
 4. Thetwo-piece fastener assembly of claim 1 wherein said fastener is a screwmember having threads thereon.
 5. A two-piece fastener assembly forsecuring two thermoplastic roof membranes to an underlying roof deckcomprising: a) a metal stress plate of ellipsoidal configuration definedby a top surface and a bottom surface having an opening in its centerportion for receiving a fastener therethrough; b) a thermoplasticcoating covering the top surface of said metal stress plate; and c) afastener positioned in said opening of said metal stress plate.
 6. Thetwo-piece fastener assembly of claim 5 wherein said metal stress plateis formed of stainless steel, galvalume or galvanized metals.
 7. Thetwo-piece fastener assembly of claim 5 wherein said thermoplasticcoating is a material selected from a group consisting of polyvinylchloride, thermoplastic olefins, chlorinated polyethylene,chlorosulfonated polyethylene, nylon and ethylene propylene dienerubber.
 8. The two-piece fastener assembly of claim 5 wherein saidfastener is a screw member having threads thereon.
 9. A two-piecefastener assembly for securing two thermoplastic roof membranes to anunderlying roof deck comprising: a) a metal stress plate of squareconfiguration defined by a top surface and a bottom surface having anopening in its center portion for receiving a fastener therethrough; b)a thermoplastic coating covering the top surface of said metal stressplate; and c) a fastener positioned in said opening of said metal stressplate.
 10. The two-piece fastener assembly of claim 9 wherein said metalstress plate is formed of stainless steel or galvanized metals.
 11. Thetwo-piece fastener assembly of claim 9 wherein said thermoplasticcoating is a material selected from a group consisting of polyvinylchloride, thermoplastic olefins, chlorinated polyethylene,chlorosulfonated polyethylene, nylon and ethylene propylene dienerubber.
 12. The two-piece fastener assembly of claim 9 wherein saidfastener is a screw member having threads thereon.
 13. The two-piecefastener assembly for securing two thermoplastic roof membranes to anunderlying roof deck comprising: a) a metal stress plate of rectangularconfiguration defined by a top surface and a bottom surface having anopening in its center portion for receiving a fastener therethrough; b)a thermoplastic coating covering the top surface of said metal stressplate; and c) a fastener positioned in said opening of said metal stressplate.
 14. The two-piece fastener assembly of claim 13 wherein saidmetal stress plate is formed of stainless steel, galvalume or galvanizedmetals.
 15. The two-piece fastener assembly of claim 13 wherein saidthermoplastic coating is a material selected from a group consisting ofpolyvinyl chloride, thermoplastic olefins, chlorinated polyethylene,chlorosulfonated polyethylene, nylon and ethylene propylene dienerubber.
 16. The two-piece fastener assembly of claim 13 wherein saidfastener is a screw member having threads thereon.
 17. A method ofsecuring a first thermoplastic roof membrane to a second thermoplasticroof membrane and securing said first and said second thermoplastic roofmembranes to an underlying roof deck comprising the steps of: 1)providing a two-piece fastener assembly comprising: a) a metal stressplate of circular configuration defined by a top surface and a bottomsurface having an opening in its center portion for receiving a fastenertherethrough; b) a thermoplastic coating covering the top surface ofsaid metal stress plate; c) a fastener positioned in said opening ofsaid metal stress plate; 2) placing said first thermoplastic roofmembrane on said roof deck; 3) placing said stress plate on a marginalportion of said first thermoplastic roof membrane; 4) inserting saidfastener through said opening in said stress plate; 5) threading saidfastener through said first thermoplastic roof membrane into said roofdeck to fasten the thermoplastic roof membrane to the roof deck; 6)placing said second thermoplastic roof membrane to overlap said stressplate and said marginal portion of said first thermoplastic roofmembrane; and 7) applying heat and pressure to the overlapped portion ofthe thermoplastic roof membranes thereby causing a fusion of the secondthermoplastic roof membrane to the stress plate and the firstthermoplastic roof membrane to provide a waterproof covering over saidroof deck.
 18. A method of securing a first thermoplastic roof membraneto a second thermoplastic roof membrane and securing said first and saidsecond thermoplastic roof membranes to an underlying roof deckcomprising the steps of: 1) providing a two-piece fastener assemblycomprising: a) a metal stress plate of ellipsoidal configuration definedby a top surface and a bottom surface having an opening in its centerportion for receiving a fastener therethrough; b) a thermoplasticcoating covering the top surface of said metal stress plate; c) afastener positioned in said opening of said metal stress plate; 2)placing said first thermoplastic roof membrane on said roof deck; 3)placing said stress plate on a marginal portion of said firstthermoplastic roof membrane; 4) inserting said fastener through saidopening in said stress plate; 5) threading said fastener through saidfirst thermoplastic roof membrane into said roof deck to fasten thethermoplastic roof membrane to the roof deck; 6) placing said secondthermoplastic roof membrane to overlap said stress plate and saidmarginal portion of said first thermoplastic roof membrane; and 7)applying heat and pressure to the overlapped portion of thethermoplastic roof membranes thereby causing a fusion of the secondthermoplastic roof membrane to the stress plate and the firstthermoplastic roof membrane to provide a waterproof covering over saidroof deck.
 19. A method of securing a first thermoplastic roof membraneto a second thermoplastic roof membrane and securing said first and saidsecond thermoplastic roof membranes to an underlying roof deckcomprising the steps of: 1) providing a two-piece fastener assemblycomprising: a) a metal stress plate of square configuration defined by atop surface and a bottom surface having an opening in its center portionfor receiving a fastener therethrough; b) a thermoplastic coatingcovering the top surface of said metal stress plate; c) a fastenerpositioned in said opening of said metal stress plate; 2) placing saidfirst thermoplastic roof membrane on said roof deck; 3) placing saidstress plate on a marginal portion of said first thermoplastic roofmembrane; 4) inserting said fastener through said opening in said stressplate; 5) threading said fastener through said first thermoplastic roofmembrane into said roof deck to fasten the thermoplastic roof membraneto the roof deck; 6) placing said second thermoplastic roof membrane tooverlap said stress plate and said marginal portion of said firstthermoplastic roof membrane; and 7) applying heat and pressure to theoverlapped portion of the thermoplastic membranes thereby causing afusion of the second thermoplastic roof membrane to the stress plate andthe first thermoplastic roof membrane to provide a waterproof coveringover said roof deck.
 20. A method of securing a first thermoplastic roofmembrane to a second thermoplastic roof membrane and securing said firstand said second thermoplastic roof membranes to an underlying roof deckcomprising the steps of: 1) providing a two-piece fastener assemblycomprising: a) a metal stress plate of rectangular configuration definedby a top surface and a bottom surface having an opening in its centerportion for receiving a fastener therethrough; b) a thermoplasticcoating covering the top surface of said metal stress plate; c) afastener positioned in said opening of said metal stress plate; 2)placing said first thermoplastic roof membrane on said roof deck; 3)placing said stress plate on a marginal portion of said firstthermoplastic roof membrane; 4) inserting said fastener through saidopening in said stress plate; 5) threading said fastener through saidfirst thermoplastic roof membrane into said roof deck to fasten thethermoplastic roof membrane to the roof deck; 6) placing said secondthermoplastic roof membrane to overlap said stress plate and saidmarginal portion of said first thermoplastic roof membrane; and 7)applying heat and pressure to the overlapped portion of thethermoplastic membranes thereby causing a fusion of the secondthermoplastic roof membrane to the stress plate and the firstthermoplastic roof membrane to provide a waterproof covering over saidroof deck.
 21. A two-piece fastener assembly for securing twothermoplastic roof membranes to an underlying roof deck comprising: 1) ametal stress plate of circular configuration defined by acircumferential edge and having a top surface and a bottom surface, andan opening in its center portion for receiving a fastener therethrough,said metal stress plate comprising: a) a first flat surface surroundingsaid opening; b) a second flat surface adjacent to said circumferentialedge; c) a third flat surface extending between said first flat surfaceand said second flat surface; d) a first circumferential portion,extending above said second flat surface and towards said third flatsurface at an angle of from about 25° to about 70°, connecting saidsecond flat surface with said third flat surface; and e) a secondcircumferential portion, extending above said first flat surface andtowards said third flat surface at an angle of from about 25° to about70°, connecting said first flat surface and said third flat surface; 2)a thermoplastic coating covering the top surface of said metal stressplate; and 3) a fastener positioned in said opening of said metal stressplate.
 22. The two-piece fastener assembly of claim 21 having a lowheight profile of from about 0.030″ to about 0.350″.
 23. The two-piecefastener assembly of claim 21 wherein said metal stress plate is formedof stainless steel or galvanized metals.
 24. The two-piece fastenerassembly of claim 21 wherein said thermoplastic coating is a materialselected from a group consisting of polyvinyl chloride, thermoplasticolefins, chlorinated polyethylene, chlorosulfonated polyethylene, nylonand ethylene propylene diene rubber.
 25. The two-piece fastener assemblyof claim 21 wherein said fastener is a screw member having threadsthereon.
 26. A two-piece fastener assembly for securing twothermoplastic roof membranes to an underlying roof deck comprising: 1) ametal stress plate of ellipsoidal configuration defined by acircumferential edge and having a top surface and a bottom surface, andan opening in its center portion for receiving a fastener therethrough,said metal stress plate comprising: a) a first flat surface surroundingsaid opening; b) a second flat surface adjacent to said circumferentialedge; c) a third flat surface extending between said first flat surfaceand said second flat surface; d) a first circumferential portion,extending above said second flat surface and towards said third flatsurface at an angle of from about 25° to about 70°, connecting saidsecond flat surface with said third flat surface; and e) a secondcircumferential portion, extending above said first flat surface andtowards said third flat surface at an angle of from about 25° to about70°, connecting said first flat surface and said third flat surface; 2)a thermoplastic coating covering the top surface of said metal stressplate; and 3) a fastener positioned in said opening of said metal stressplate.
 27. The two-piece fastener assembly of claim 26 having a lowheight profile of from about 0.030″ to about 0.350″.
 28. The two-piecefastener assembly of claim 26 wherein said metal stress plate is formedof stainless steel or galvanized metals.
 29. The two-piece fastenerassembly of claim 26 wherein said thermoplastic coating is a materialselected from a group consisting of polyvinyl chloride, thermoplasticolefins, chlorinated polyethylene, chlorosulfonated polyethylene, nylonand ethylene propylene diene rubber.
 30. The two-piece fastener assemblyof claim 26 wherein said fastener is a screw member having threadsthereon.
 31. A two-piece fastener assembly for securing twothermoplastic roof membranes to an underlying roof deck comprising: 1) ametal stress plate of square configuration defined by a circumferentialedge and having a top surface and a bottom surface, and an opening inits center portion for receiving a fastener therethrough, said metalstress plate comprising: a) a first flat surface surrounding saidopening; b) a second flat surface adjacent to said circumferential edge;c) a third flat surface extending between said first flat surface andsaid second flat surface; d) a first parametrical portion, extendingabove said second flat surface and towards said third flat surface at anangle of from about 25° to about 70°, connecting said second flatsurface with said third flat surface; and e) a second parametricalportion, extending above said first flat surface and towards said thirdflat surface at an angle of from about 25° to about 70°, connecting saidfirst flat surface and said third flat surface; 2) a thermoplasticcoating covering the top surface of said metal stress plate; and 3) afastener positioned in said opening of said metal stress plate.
 32. Thetwo-piece fastener assembly of claim 31 having a low height profile offrom about 0.030″ to about 0.350″.
 33. The two-piece fastener assemblyof claim 31 wherein said metal stress plate is formed of stainless steelor galvanized metals.
 34. The two-piece fastener assembly of claim 31wherein said thermoplastic coating is a material selected from a groupconsisting of polyvinyl chloride, thermoplastic olefins, chlorinatedpolyethylene, chlorosulfonated polyethylene, nylon and ethylenepropylene diene rubber.
 35. The two-piece fastener assembly of claim 31wherein said fastener is a screw member having threads thereon.
 36. Atwo-piece fastener assembly for securing two thermoplastic roofmembranes to an underlying roof deck comprising: 1) a metal stress plateof rectangular configuration defined by a circumferential edge andhaving a top surface and a bottom surface, and an opening in its centerportion for receiving a fastener therethrough, said metal stress platecomprising: a) a first flat surface surrounding said opening; b) asecond flat surface adjacent to said circumferential edge; c) a thirdflat surface extending between said first flat surface and said secondflat surface; d) a first parametrical portion, extending above saidsecond flat surface and towards said third flat surface at an angle offrom about 25° to about 70°, connecting said second flat surface withsaid third flat surface; and e) a second parametrical portion, extendingabove said first flat surface and towards said third flat surface at anangle of from about 25° to about 70°, connecting said first flat surfaceand said third flat surface; 2) a thermoplastic coating covering the topsurface of said metal stress plate; and 3) a fastener positioned in saidopening of said metal stress plate.
 37. The two-piece fastener assemblyof claim 31 having a low height profile of from about 0.030″ to about0.350″.
 38. The two-piece fastener assembly of claim 31 wherein saidmetal stress plate is formed of stainless steel, galvalume or galvanizedmetals.
 39. The two-piece fastener assembly of claim 31 wherein saidthermoplastic coating is a material selected from a group consisting ofpolyvinyl chloride, thermoplastic olefins, chlorinated polyethylene,chlorosulfonated polyethylene, nylon and ethylene propylene dienerubber.
 40. The two-piece fastener assembly of claim 31 wherein saidfastener is a screw member having threads thereon.
 41. A method ofsecuring a first thermoplastic roof membrane to a second thermoplasticroof membrane and securing said first and second thermoplastic roofmembranes to an underlying roof deck comprising the steps of: 1)providing a two-piece fastener assembly comprising: a metal stress plateof circular configuration defined by a circumferential edge and having atop surface and a bottom surface, and an opening in its center portionfor receiving a fastener therethrough, said metal stress platecomprising: a) a first flat surface surrounding said opening; b) asecond flat surface adjacent to said circumferential edge; c) a thirdflat surface extending between said first flat surface and said secondflat surface; d) a first circumferential portion, extending above saidsecond flat surface and towards said third flat surface at an angle offrom about 25° to about 70°, connecting said second flat surface withsaid third flat surface; and e) a second circumferential portion,extending above said first flat surface and towards said third flatsurface at an angle of from about 25° to about 70°, connecting saidfirst flat surface and said third flat surface; 2) a thermoplasticcoating covering the top surface of said metal stress plate; and 3) afastener positioned is said opening of said metal stress plate; 4)placing said first thermoplastic roof membrane on said roof deck; 5)placing said stress plate on a marginal portion of said firstthermoplastic roof membrane; 6) inserting said fastener through saidopening in said stress plate; 7) threading said fastener through saidfirst thermoplastic roof membrane into said roof deck to fasten thethermoplastic roof membrane to the roof deck; 8) placing said secondthermoplastic roof membrane to overlap said stress plate and saidmarginal portion of said first thermoplastic roof membrane; and 9)applying heat and pressure to the overlapped portion of thethermoplastic roof membranes thereby causing a fusion of the secondthermoplastic roof membrane to the stress plate and the firstthermoplastic roof membrane to provide a waterproof covering over saidroof deck.
 42. A method of securing a first thermoplastic roof membraneto a second thermoplastic roof membrane and securing said first andsecond thermoplastic roof membranes to an underlying roof deckcomprising the steps of: 1) a metal stress plate of ellipsoidalconfiguration defined by a circumferential edge and having a top surfaceand a bottom surface, and an opening in its center portion for receivinga fastener therethrough, said metal stress plate comprising: a) a firstflat surface surrounding said opening; b) a second flat surface adjacentto said circumferential edge; c) a third flat surface extending betweensaid first flat surface and said second flat surface; d) a firstcircumferential portion, extending above said second flat surface andtowards said third flat surface at an angle of from about 25° to about70°, connecting said second flat surface with said third flat surface;and e) a second circumferential portion, extending above said first flatsurface and towards said third flat surface at an angle of from about25° to about 70°, connecting said first flat surface and said third flatsurface; 2) a thermoplastic coating covering the top surface of saidmetal stress plate; and 3) a fastener positioned is said opening of saidmetal stress plate; 4) placing said first thermoplastic roof membrane onsaid roof deck; 5) placing said stress plate on a marginal portion ofsaid first thermoplastic roof membrane; 6) inserting said fastenerthrough said opening in said stress plate; 7) threading said fastenerthrough said first thermoplastic roof membrane into said roof deck tofasten the thermoplastic roof membrane to the roof deck; 8) placing saidsecond thermoplastic roof membrane to overlap said stress plate and saidmarginal portion of said first thermoplastic roof membrane; and 9)applying heat and pressure to the overlapped portion of thethermoplastic roof membranes thereby causing a fusion of the secondthermoplastic roof membrane to the stress plate and the firstthermoplastic roof membrane to provide a waterproof covering over saidroof deck.
 43. A method of securing a first thermoplastic roof membraneto a second thermoplastic roof membrane and securing said first andsecond thermoplastic roof membranes to an underlying roof deckcomprising the steps of: 1) providing a two-piece fastener assemblycomprising: a metal stress plate of square configuration defined by acircumferential edge and having a top surface and a bottom surface, andan opening in its center portion for receiving a fastener therethrough,said metal stress plate comprising: a) a first flat surface surroundingsaid opening; b) a second flat surface adjacent to said circumferentialedge; c) a third flat surface extending between said first flat surfaceand said second flat surface; d) a first parametrical portion, extendingabove said second flat surface and towards said third flat surface at anangle of from about 25° to about 70°, connecting said second flatsurface with said third flat surface; and e) a second parametricalportion, extending above said first flat surface and towards said thirdflat surface at an angle of from about 25° to about 70°, connecting saidfirst flat surface and said third flat surface; 2) a thermoplasticcoating covering the top surface of said metal stress plate; 3) afastener positioned is said opening of said metal stress plate 4)placing said first thermoplastic roof membrane on said roof deck; 5)placing said stress plate on a marginal portion of said firstthermoplastic roof membrane; 6) inserting said fastener through saidopening in said stress plate; 7) threading said fastener through saidfirst thermoplastic roof membrane into said roof deck to fasten thethermoplastic roof membrane to the roof deck; 8) placing said secondthermoplastic roof membrane to overlap said stress plate and saidmarginal portion of said first thermoplastic roof membrane; and 9)applying heat and pressure to the overlapped portion of thethermoplastic roof membranes thereby causing a fusion of the secondthermoplastic roof membrane to the stress plate and the firstthermoplastic roof membrane to provide a waterproof covering over saidroof deck.
 44. A method of securing a first thermoplastic roof membraneto a second thermoplastic roof membrane and securing said first andsecond thermoplastic roof membranes to an underlying roof deckcomprising the steps of: 1) providing a two-piece fastener assemblycomprising: a metal stress plate of rectangular configuration defined bya circumferential edge and having a top surface and a bottom surface,and an opening in its center portion for receiving a fastenertherethrough, said metal stress plate comprising: a) a first flatsurface surrounding said opening; b) a second flat surface adjacent tosaid circumferential edge; c) a third flat surface extending betweensaid first flat surface and said second flat surface; d) a firstparametrical portion, extending above said second flat surface andtowards said third flat surface at an angle of from about 25° to about70°, connecting said second flat surface with said third flat surface;and e) a second parametrical portion, extending above said first flatsurface and towards said third flat surface at an angle of from about25° to about 70°, connecting said first flat surface and said third flatsurface; 2) a thermoplastic coating covering the top surface of saidmetal stress plate; and 3) a fastener positioned is said opening of saidmetal stress plate; 4) placing said first thermoplastic roof membrane onsaid roof deck; 5) placing said stress plate on a marginal portion ofsaid first thermoplastic roof membrane; 6) inserting said fastenerthrough said opening in said stress plate; 7) threading said fastenerthrough said first thermoplastic roof membrane into said roof deck tofasten the thermoplastic roof membrane to the roof deck; 8) placing saidsecond thermoplastic roof membrane to overlap said stress plate and saidmarginal portion of said first thermoplastic roof membrane; and 9)applying heat and pressure to the overlapped portion of thethermoplastic roof membranes thereby causing a fusion of the secondthermoplastic roof membrane to the stress plate and the firstthermoplastic roof membrane to provide a waterproof covering over saidroof deck.